Self-limiting electrolytic heater

ABSTRACT

An electrolytic heater especially adapted to deaerate water by a process in which water is heated to form steam and is counterflowed against the rising steam to strip air from the water. The heater includes an open container divided by a perforated wall into upper and lower chambers and electrodes located in the lower chamber. Water is introduced into the upper chamber, passes through the openings in the wall to the lower chamber where it is heated electrolytically to form steam and from which deaerated water is withdrawn. Steam and water are required to flow in opposite directions through the same openings in the dividing wall so that the flow of each is an inverse function of the other and a balance will be reached automatically limiting the liquid level in the lower chamber and the rate of steam generation resulting from current flow between electrodes.

United States Patent Rodgers [54] SELF-LIMITING ELECTROLYTIC [1513,685,259 [451 Aug. 22, 1972 HEATER Primary Examiner-Reuben Friedman[72] Inventor: Franklin A. R e B kl' Assistant Burks Mm meAttorney-Brown and Mikulka and Robert E. Corb [73] Assignee: 'fitctideCorporation, Cambridge, [57] ABSTRA T I ass. An electrolytic heaterespecially adapted to deaerate [22] Flled: May 10, 1971 water by aprocess in whichwater is heated to form 21 1 41 73 steam and iscounterflowed against the rising steam to strip air from-the water. Theheaterincludes an open v container divided by a perforated wall intoupper and 1 iq 33 lower'chambers and electrodes located in the lower[58] i 4 198 chamber. Water is introduced into the upper chamber,215/275 2 passes through the openings in the wall to the lower I chamberwhere it is heated electrolytically to form [56] References Cited steamand from which deaerated water is withdrawn Steam and water are requiredto flow in opposite UNITED STATES PATENTS directions through the sameopenings in the dividing wall so that the flow of each is an inversefunction of gg v the other and a balance will be reached automatically3488474 1/1970 sauriiers 219/284 limiting the liquid level in the lowerchamber and the rate of steam generation resulting from current flowFOREIGN PATENTS OR APPLICATIONS between electrodes- 4l4,388 7/1934 GreatBritain ..2l9/284 5 Claims, 1 Drawing Figure as is l f V M l2 OVERFLOW gINLET O 9 O 3 TL 24 o 6 O 0 re O ts 2 l. IO

NtNfiiNNNNHNk Ht 34 I4 20 34 SELF -LIMITING ELECTROLYTIC HEATERElectrolytic heaters are well known devices for heating liquids,particularly water, and generally comprise a pair of electrodes adaptedto be immersed in a liquid such as water which containsimpurities,particularly electrolytes, which render the liquid between theelectrodes electrically conductive. The current flowing through the highimpedance electrical path provided by the water, causes the water to beheated at a rate dependent upon the current flow rate. Thus the currentflow rate and heating rate can be varied by changing the area of theelectrodes immersed in the conductive liquid. This is accomplished bymoving the electrodes and/or by altering the level of the liquid inwhich electrodes are immersed. Other systems for controlling the heatingrate involve varying the electrical potential between the electrodes soasto control the current flow and/or varying the spacing betweenelectrodes so as to control the length and hence, resistance, of theconductive path provided by the conductive liquid.

The present invention has as an object the provision of a simple andinexpensive system having no moving parts for automatically controllingthe level of the conductive liquid in which the electrodes are immersedas a function of the rate of vapor (e.g. steam) formation.

A conventional liquid degassing process particularly useful in thedeaeration of water involves heating the water to form steam andcounterflowing the water in intimate contact with the heated vapor orsteam which strips the liquid of the air. A typical water deaerationboiler comprises an open container for holding a column of waterincluding means for heating the lower portion of the column of water andprovision for causing the water to flow downward against the risingsteam. Frequently the column is filled with packing elements designed toform tortuous passages for causing more intimate contact between thecounterflowing water and steam. Deaerator boilers of this type areusually operated such that a very small amount of steam continuouslyescapes from the surface of the column of water thereby assuringcomplete deaeration without waste of steam and the heat energy requiredto produce it. In deaeration systems wherein the rate of flow of liquidthrough the deaerator boiler, electrical potential, feed watertemperature, etc. are subject to change, complex controls have beenprovided for varying the heat input so as to maintain the rate of escapeof excess steam at a constant predetermined value, assuring completedeaeration while maintaining energy loss at a minimum.

Another object of the present invention is to provide anelectrolytically heated, deaerator boiler of the type described in whicha balance is achieved between steam generation and water flow toautomatically control the amount of steam escaping so that it remainssubstantially constant despite fluctuations in other variables such asthe rate of flow of liquidthrough the deaerator.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the apparatus possessing theconstruction, combination of elements and arrangement of parts which areexemplified in the following detailed disclosure, and the scope of theapplication of which will be indicated in the claims.

from the water. The deaerator boiler generally comprises an opencontainer 10 for holding a' column of -water withprovision forcirculating the water downwardly within the container or column. In thesimplest form shown, these last-mentioned means com- .prise an inletopening 12 near the upper extremity of the container and an outletopening 14 in the lower part of the container. The outlet opening may belocated in the bottom wall of the container as shown in the drawing topermit complete drainage of the container or it may be located above thebottom wall so that a quantity of liquid always remains in thecontainer. In the form shown, container 10 is preferably rectangular andincludes planar side walls 16, end walls 18 and a rectangular bottomwall 20, cooperating to form a chamber open at the top. A dividing wall22 is secured to the end and side walls to separate the container intoan upper chamber designated 24 and a lower chamber designated 26.Dividing wall 22 is formed with openings or passages 28 through whichwater introduced into upper chamber 24 is conducted to lower chamber 26and through which steam formed in lower chamber 26 passes into upperchamber 24. Dividing wall 22 is joined to the end and side walls of thecontainer so that substantially all of the steam and water are requiredto pass in opposite directions through openings 28.

Mounted within lower chamber 28 are a pair of electrodes in the form ofplates 30 and 32 located in substantia'lly parallel spaced relation andelectrically isolated from one another and container 10 by insulatingmounts 34. Plates 30 and 32 are connected by suitable leads 36 to asource of electric current for producing a potential across the plates.

In the operation of the deaerator boiler, water is introduced into upperchamber 24 through inlet 12 and is preferable maintained at apredetermined level by conventional means such as, for example, anoverflow outlet 38. The water flows downwardly through openings 28 intochamber 26 where it forms a high impedance electrical pathway betweenelectrode plates 30 and 32. Electric current flows across this highimpedance electrical path provided by the water thus heating the waterto form steam which passes upwardly through openings 28 into upperchamber 24. The rate of current flow and hence the rate of steamgeneration is a direct function of the level of water by varying thewater level of water in lower chamber 26 and this can be varied, byvarying the water level.

As previously noted, the optimum operating condition is one in whichsteam is generated at a rate such that a very small amount escapes fromthe surface of the water within upper chamber 24. If no steam escapesthen it is probable that deaeration will not be complete while on theother hand, a relatively large amount of escaping steam representswasted energy. The rate of steam generation required to maintain thisoptimum operating condition is, of course, a function of the rate offlow of water into and from the boiler since more steam will be requiredto deaerate an increased amount of water.

In accordance with the invention, this optimum operation condition isautomatically maintained with a simple structure having no-moving parts.Automatic control is achieved by virtue of the fact that water and steamare required to flow in opposite directions through openings 28 individing wall 22. Thus, if the amount of water withdrawn through outlet14 is increased the level of water in lower chamber 26 will be reducedthereby reducing the electrical energy input and the amount of steamgenerated and passing upwardly through openings 28. Reduction in therate of flow of steam through openings 28 permits water to flowdownwardly through the openings at a faster rate tending to restore thewater level within the lower chamber and increase electrical energy flowand steam output tending to restore the balance between water flow andsteam generation. The rate of flow of water downward through openings 28is also a function of hydrostatic pressure hence the provision ofoverflow 38 for maintaining a constant head of water in the upperchamber. Thus it will be apparent that a balance will be achievedbetween counterflow of water and steam through openings 28 for anyparticular combination of hydrostatic head number and size of openingsand rate of water flow through the deaerator boiler.

While the deaeration system of the invention has been illustrated asincluding an upper chamber 24 containing only water through which steampasses upwardly, it should be understood that the upper chamber may alsocontain conventional packing elements of a type well known in the .artwhich provide tortuous counterflow paths for steam and water producing amore intimate contact and intermixing of the steam and water as theyflow in opposite directions. This is desirable because the steamcollects the noncondensible gasses stripping them from the watersolution and the more intimate and thorough the contact between steamand water, the more rapid and complete the stripping operationperformed.

The novel, self-limiting electrolytic deaerator boiler of the inventionnot only balances steam generation against rate of water flow throughthe deaerator but also may be employed to control the rate of waterflow. Control over rate of water flow coupled with steam generationcontrol may be achieved by controlling the size and number of openings28 in dividing wall 22 and/or by altering the height of the head ofwater in upper chamber 24. Larger and/or more numerous openings willpermit higher water and steam flow rates while the opposite will beachieved by reducing the size or number of openings.

To facilitate the alteration of the balance between steam generation andwater flow and/or the rates of each, dividing wall 22 may be constructedso as to be movable upwardly or downwardly to change the volume of upperand lower chambers 24 and 26. It is also possible to provide means suchas two relatively asasfin tfizrta zr lrrrisrsrs a theza srg throughwhich water and steam are required to flow in opposite directions. Inthis way it is unnecessary to em- .ploy other means for varying steamgeneration such as mechanically or physically changing the areas ofelectrode plates 30 and 32 immersed in the liquid, or

changing the electrical potential across or the spacing between theelectrodes as is suggested inv the prior art.

Since'certain changes may be made in the above apparatus withoutdeparting from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not ina limiting sense.

lclaim:

1. A self-limiting, electrolytic heater comprising in combination:

an open container for holding a liquid;

a wall dividing said container into upper and lower chambers, said wallbeing formed with openings for permitting the passage of fluids betweensaid upper and lower chambers;

means for introducing liquid into said upper chamber;

means for withdrawing liquid from said lower chamber; and

electrodes mounted in spaced relation in said lower chamber for heatingliquid contained therein, said openings being dimensioned topredeterminedly limit the rate of flow of fluids between said chambers.

2. An electrolytic heater as defined in claim 1 including means forcontrolling the level of liquid in said upper chamber.

3. An electrolytic heater as defined in claim 1 wherein said wall ismovable to vary the depth of said chambers and the distance between saidwall and the upper extremeties of said electrodes.

4. An electrolytic heater as defined in claim 1 wherein said upperchamber is packed to form tortuous flow paths providing improved contactbetween downward flowing liquid and the rising, heated vapor thereof.

5 An electrolytic heater as defined in claim 1 wherein substantially theonly passages for the flow of liquid and the vapor thereof between saidupper and lower chambers are said openings in said wall.

1. A self-limiting, electrolytic heater comprising in combination: anopen container for holding a liquid; a wall dividing said container intoupper and lower chambers, said wall being formed with openings forpermitting the passage of fluids between said upper and lower chambers;means for introducing liquid into said upper chamber; means forwithdrawing liquid from said lower chamber; and electrodes mounted inspaced relation in said lower chamber for heating liquid containedtherein, said openings being dimensioned to predeterminedly limit therate of flow of fluids between said chambers.
 2. An electrolytic heateras defined in claim 1 including means for controlling the level ofliquid in said upper chamber.
 3. An electrolytic heater as defined inclaim 1 wherein said wall is movable to vary the depth of said chambersand the distance between said wall and the upper extremeties of saidelectrodes.
 4. An electrolytic heater as defined in claim 1 wherein saidupper chamber is packed to form tortuous flow paths providing improvedcontact between downward flowing liquid and the rising, heated vaporthereof.
 5. An electrolytic heater as defined in claim 1 whereinsubstantially the only passages for the flow of liquid and the vaporthereof between said upper and lower chambers are said openings in saidwall.